Optical projection and registration system



Feb 23, 1954 w. H. CHERRY 2,669,900

OPTICAL PROJECTION AND REGISTRATION SYSTEM Filed Feb. l, 1949 naif/rm if 7g' 77 Z4 Patented Feb. 23, 1954 OPTICAL PROJECTION AND REGISTRATION SYSTEM William H. Cherry,

Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application February 1, 1949, Serial No. 73,877

8 Claims. 1

This invention relates to optical systems and more particularly to arrangements for controlling optical registration of a plurality of images.

When it is desired to optically register differently positioned points of light or diiferent images such as selected component color images, it is often necessary to carefully adjust the relative positions of the projected images and to independently control the sizes of the individual projected images.

This, of course, can be accomplished by changing the position of the image or point of light source. Such changes may not only be diicult and complexbut may tend toward interference with detail and other undesirable eects. It is therefore desirable that the light source remain substantially fixed and that an optical arrangement be provided in each of the light paths to independently control the position and the size of the projected images. Although changing the position of the cooperating lens system will to some extent permit adjustment, there are often additional adjustments necessary which cannot be made by an adjustment of the lens system.

Many ingenious devices have been suggested in the field of optical range iinding for accomplishing parts of this requirement. For example, it has been proposed to employ a pair of prisms, movable with respect to each other, to change one of a pair of light paths where a pair of images must be registered.

Such an arrangement although generally satisfactory for range nders, is not particularly suitable when dealing with separated component color images such as, for example, the component color images employed in color television. The effect of prisms to chromatically distort images is quite Well known to the art. The cost and bulk of the prisms in such applications are often prohibitive.

According to the present invention a pair oi transparent elements such as glass plates having parallel surfaces are positioned in the optical path between a point or image source and its projected image and by providing mechanical positioning devices so that the plates may be rotated about aries lying parallel to the plates and axes lying parallel to the object-image direction, it is possible, through the rotation of such plates, to displace the apparent or eiective optical position of the projected image either laterally or longitudinally, separately, or both together without otherwise distorting, magnifying, or rotating the object or image planes. Not only can the obvious lateral displacements necessary to registration be achieved without complicated mechanical or electro-magnetic adjustments, but also by changing the eifective object and/or image distance the magnification can be changed even though the image source position and the viewing screen are both fixed.

rI'he effect of the rotation of the transparent elements is not very large so extremely line Vernier adjustments are possible with very crude mechanical arrangements.

A primary object of this invention is to provide an improved optical system for controlling each light path of a multiple optical system.

Another object of this invention is to provide for convenient registration of a plurality of images.

Another object of this invention is to secure the apparent displacement in face by simple means of the optical position of objects or images for the purpose of focussing, changing magnification or changing position of one or more points of light or images.

Other and incidental objects of the invention will be apparent to those skilled in the art from a reading of the following specification and an inspection of the accompanying drawing in which:

Figure l illustrates schematically the bending of a light ray when passing through two parallel surfaces of a transparent element having a refractive index differing from that of air;

Figure 2 illustrates the application of this invention in one of its simplest forms for the lateral displacement of one optical image with respect to another image for purposes of registration;

Figure 3 illustrates the application or" this invention in one of its simplest forms for the longitudinal displacement of one optical image with respect to another` image for purposes of registration; and,

Figure 4 shows schematically this invention in another of its forms involving a color television system.

Turning now in more detail to Figure l there is shown an element i having parallel sides and having a refractive index greater than unity.

It will be seen that as light approaches along the path 3 it is bent upon entering the rst face of element l and it is bent baci: to its original direction on leaving the element l at the opposite face and follows the path It will, of course, be seen that if the element I were not in the light path or if the light path 3 intercepted the faces of element perpendicularly, the light traveling along light path 3 would continue along the dotted line i.

Turning to Figure 2 there is shown, by way of 3 example, kinescopes 9 and Il or other image forming devices together with their associated projecting lenses I3 and i5.

The light path from kinescope il is indicated by line I1 and as will be seen by inspection,` is not interrupted until. it arrives in the focussing plane I9.

In the light path 2| of kinescope 9 there is positioned, however, a pair of elements 23 and 25, each such as illustrated in Figure 1.

If it were not for the elements 2'3 and 25, the kinescope 9 in connection with its lens I3 might produce, because of other mechanical details ciV arrangement or imperfection,v anima-ge 2,1 which.. as indicated, does not coincide with or correspond to the image i9 projected by lens `|5from kinescope ll. This failure to coincide may be maniu fest in that the tWo images are laterally displaced from one another in the same image plane, or` inv-that the two, image planes, the one of. kinescope. liandlens l5, and the other of kinescope 9- and lens i3, doi not coincide but are displaced longitudinally backward or foiwardwith respect to one another or combinations ofbotheiiects. It isonly the first possibility which is intended' to be. illustrated in this Figure 2.

It is assumed in this explanationof Figurel 2V that the sizes of the twov imagesarealreadyad justed to be correct, either thesame to secure complete registry, `or inl Whateverfproportion required in the-use of the optical apparatusde` scribed. Since, as-is-wellknown, suchadjustment can always be accomplishedv by the longitudinal motion of one of the lenses, or other means, this present assumption for of explanation does not constitute a limitation on. the' applicability ofv `the present invention.

Now by properly rotatingfthe'elements 23 and 25-the light path, 2|v may be displaced to afposition along line 29 in order that thefimage of the image forming kinescope- 9 Will be projectedso asI to coincide withthe image' I3-of the image forming kinescope LI. In this case of FiguraZ, Wherenonly a lateral displacement ot the one image is required, it is 23` and, 25- be xed atf suitable inclinations to the opticalx axis 2d and' befseparately rotated about that.- axis :so asi to 'accomplish the desired adjustment.

Inl Figure f3: therel is illustrated an' arrangement forA changing the-,length 'of-the optical'paths; or

the .purposes .of clarity preferable that elements n ohanginggt'he optical l size-of the imageA without the: adjustment 0fthe1kinescopes-3lr or 33. In Figure' the: elementsy 35 and: 31 yare .adjusted-rat an ang-lef so: that the.. optical: path: represented; by.V

linez39=l corresponds. in positionto line'M'. It'Will be. noted, however, that theiopticalpath v13 be-f tween elements 35 and 31 is displaced.; Inthisv mannerthe lengtheof' the: optical: path` mayfbe increased Withlrespectitoithe overallpa'raxial'distance between kinescope 3l and its image 45; vBy decreasing the mechanical -paraxial distanceibetween the object andiitslimage'; Whileholdingithe optical path lengthand hence also.tlfieimagnifica tion constant, the position-ofi thelimageid' will bemade tov coincideWith-the plane of the? image 41 which may be` the same plane.y as thaty image planerof the image forming' kinescop'ely 33.

It can be seen therefore'in an inverse manner` thaty the size of theimages produced-bykinescopes 3l andA 33- may be independently changed by manipulationl 0f` the lenses 49 and 5I. Yetiby additional'v manipulation of the elements' 3'5 and' 31, the image planes 'may'yet' beinadeltbc'oineide.- It'is'true-that in'this manner-'magnification can 'rotations' of el'ern'eiritsA 23 and be varied usually only a small amount, but it is often true that only a small amount of variation is required to obtain registry. The sharper these inclinations, and the greater the optical thickness of the elements 23 and 25, the greater will be the image-displacement which can be effected by this adjustment. So long asthe axialinclinations of the elements 23 and 25 are held fixed, no change iniv the paraxial path length from image forming kinescope 9 to image 21 Will occur in the axial 25. Since, however, the initial insertion of elements 23 and 25 does changer this pathl length, it is sometimes desirable toinsertel'e'ments" (not shown) similar to 23 and 25 and preferablyat similar axial inclinations, but not necessarily rotatable about the optical axis, into the optical path l1 so as to effect an equal. initial change of path length in path I1.

The circumstances described in Figures 2 and 3 are obviously special cases or" non-coincidenceof two optical images, which, after their relative sizesv have beeny corrected, as by Well. known rriethfr ods,A may bestillsnon-coincident by virtue ofboth lateral. and longitudinal displacements simultane-i ously. It should. now be clear that both of these displacements: can' be accountedy for simultane-A ously by combination of the. two types of adjust-j ments described in `connection with Figurev 2land Figure 3, respectively, both types ofadjustments preferably operating on the saine pair ofcompensating-elements,v each like i of- Figure-.1f and' mounted. so that both their angles of` inclination to the opticala-xis andtheir azimuths of-.rotationabout that axis maybeadjusted independently TurningnoW in detailito Figurel-,f there isillusi tratedr a color television receiver-53;: Thecolor television receiver may-take the formof any well known types suchas for example, that included.y inthe description of. a simultaneoustype color television system in the article entitled SimultaneousAll ElectronfGolor Television beginning on ,page '459' of RCA Review vfor December 1946 or the: article-i entitled AnA yExperimental Sir-nul-r tan'eousfColor System beginningvon page-861 of the Proceedings of the InstituteI of RadiovEngiz neersffor September 194i?.`

In thef articles referred. to:` immediately above, there is illustrated av simultaneousicolorvtelevisionreceive'r' yincluding` selected component color image forming kinescopes 55, F11-,and Sii-,togetherwiththeir projection lenses4 6i, 63,', and--65and their assocatedfcolorlters 56;:58 and 60'.

Although theftheory upon Whichthecolor tele visioniofthis sortioperatesfis adequately described in the articles-refrred to, thetheory of operationwill 'befbriefly outlined :in order Vtoprcvide for a complete understanding of thisinvention.

As isw'ellrknown'totheopticalfart a' color imagel may be reproduced by dividing the color fromithe' object intofseveralI .different selectedI` component colorsfsuch asrred, blue'andgreen.Y 2in-accorde ancea with .normalitelevision lprocedure each-'ofI the several:v differentv componentfcolors m'ayffbe transformed into electrical information and transmitted to a". remote location; The electrical information `may then be reconvert`edrintoI an opticalimage representativefof the respectivezsea' lecte'd component colori. The :severalcomponent color images may then' b'eM combined'L in registry` toformamaterialcolorlimage;

lAs WasVA 'indicated' above,4 it' is, .of course nec essary' to obtainaaccurate registry' when'. combiming the several images t'oiform atcompositefimage In'theillustrationlofi-Figure42tlieiseveralidifferentpossibilities'ofch'angefare illustrated;`

For example, the light, the red colored image from the kinescope 55, and filter 56 is transmitted through the elements B1 and 69 which are positioned with respect to each other to change the path length in order to correct for error in image size.

The green image from kinescope 51 and lter 58, however, is transmitted along its optical path without change by positioning the elements il and 13 in a parallel position and in a position such that the light intercepts it at substantially a right angle.

The blue light image from kinescope 59 and filter 60, however, is displaced by the proper positioning of elements 15 and T! as explained in Figure 2 above. Such correction permits light from the corresponding point on each of the kinescopes 55, 51, and 59 to register at point 19.

Having thus described the invention what is claimed is:

l. An optical system for registering two points of light at an imaging point comprising a pair of point of light sources, a plurality of clear elements each having refractive indices differing from the refractive index of air and each transparent element having two parallel surfaces through which the same and substantially all the light will pass from only one of said light sources, and means for tilting each of said transparent elements, with respect to each other and with respect to said last referenced light source to independently change the effective optical distance between the light source last referred to and said imaging point and to change the position of the imaging point of said last referenced light source.

2. An optical system for registering two points of light at an imaging point comprising a pair of point of light sources, a lens system positioned to focus said points of light substantially in registry at said imaging point, a plurality of transparent elements each transmitting the entire visual spectrum substantially uniformly and each having refractive indices differing from the refractive index of air and each transparent element having two parallel surfaces through which the same light and substantially all the light will pass from only one of said light sources, and means for tilting said transparent elements with respect to each other and with respect to said last referenced light source to change the focal distance of said optical system and to change the position of the imaging point of said last referenced light source.

3. An optical system comprising a pair of light point sources, a lens system positioned to focus said points of light substantially in registry at said imaging point, a pair of neutral transparent elements each having refractive indices differing from the refractive index of air and each transparent element having two parallel surfaces, both of said transparent elements positioned in a direct line between one of said light point sources and said imaging point and means for tilting each of said elements with respect to the optical path between said light sources and said imaging point and with respect to said last referenced light source to independently change the effective length of said optical path and to change the position of the imaging point of said last referenced light source.

4. An optical system for registering two points of light at an imaging point comprising a pair of light point sources, a lens system positioned to focus said points of light substantially in registry at said imaging point, a pair of transparent elements each having refractive indices differing from the refractive index of air and each transparent element having two parallel surfaces, said transparent elements positioned in a single light path and between one of said light point sources and said imaging point, and means for rotating each of said transparent elements about a line in their plane and with respect to said last referenced light source to independently change the relative optical path length of the paths of light with respect to each other and to change the position of the imaging point of said last referenced light source.

5. An arrangement for registering images in an imaging plane comprising a pair of light image sources, an optical system positioned to focus said images substantially in registry in said imaging plane, a pair of clear, light transmitting elements each having refractive indices .differing from unity and each transparent element having two parallel light transmitting surfaces, said transparent elements positioned in one light path and between one of said light image sources and said imaging plane and wherein each of said transparent elements are rotatable about a line in their plane and wherein said lines are parallel to change the relative effective optical path length and the relative position of the images in said image plane independently of` each other.

6. An arrangement for registering images in an imaging plane comprising a pair of light image sources, an optical system positioned to focus said images substantially in registry in said given plane, a pair of transparent elements each having equal refractive indices differing from unity and each transparent element having two parallel surfaces, said transparent elements positioned in line and between one of said light image sources and said imaging plane, and means for rotating the plane of each of said transparent elements to change the effective optical path length between said light image sources and said image plane and to change the relative positions of said images on said imaging plane independently of f1 the change in effective optical path length.

7. An optical system comprising in combination a plurality of light image sources, an imaging screen, a lens system in cooperative positioning with said light image sources to project the light images of said sources on said imaging screen in substantial registry, a separate pair of transparent elements positioned in at least all but one light path between said light image sources and said imaging screen, said transparent elements each having two parallel surfaces through which the light is directed and wherein the refractive indices of said transparent elements differ from unity, means for rotating said elements about parallel lines to control the relative effective optical path length of said light paths and the relative position of the light images on said imaging screen.

3. A color television image reproducing system having an arrangement for registering a plurality of diderent component color images comprising in combination, sources of said different component color images, a lens system positioned t0 focus said different component color images substantially in registry in a given plane, a plurality of clear elements each having refractive indices differing from unity and each transparent element having two parallel surfaces, a different pair of said clear elements positioned in the same light path between each of said images and said imaging plane, and means for changing the effecmassimo:

'Rferenmw Gitedz vin chxaulea of. thssfpatent' Name Date Ives Jiuly 22,.I 189@ Ball? eml aI. June 1925 Number Number Sisson JJwIY'fB-w 

